RigidBody3D slows down before hitting "ground"

Question

I have a simple scene set up using Bullet physics with a RigidBody3D falling down and hitting another RigidBody3D representing the ground. All settings are default besides the extents of the rigid bodies collision shapes. A CSGBox is used to give me a visual representation of the rigid body.

Before the falling rigid body hits the ground it slows down, which you can see very clearly when viewing this video at 0.25 speed https://www.youtube.com/watch?v=5eZtmJjmYtI

Is my setup off? Here's an screenshot of the scene https://imgur.com/a/iUXz7bx

EDIT: My extents are 0.1 x 1.0 x 0.1. I've noticed that when using 0.2 x 1.0 x 0.2 the simulation seems to work a bit better, but surely 0.1 isn't so small that it should cause physics issues?

EDIT 2: It seems tied to the extents of the collision shape and the rotation of it. I made a video showing the problem here https://www.youtube.com/watch?v=MQJDtIkY0Ts. Am I doing something weird or is the engine?

Comments

This is whack as hell. I can reproduce it and I don't understand it either. What you're doing seems fine. If you switch to GodotPhysics it doesn't happen, but GodotPhysics has its own issues. It's gotta be an issue in bullet, I'll see if I can find an opened bug report concerning this.

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I couldn't find a bug report on this which is pretty weird (should be a common bug since I reproduced it immediately), so I opened one: https://github.com/godotengine/godot/issues/55320

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I couldn't express it better myself! Thank you for taking the time to look for and create an issue.

Answer 1

Bug in the engine and an issue was created by Bernard Courier https://github.com/godotengine/godot/issues/55320